Curing of poly



2,984,655 CURING F POLY(VINYL METHYL ETHER) David C. Kirk, Jr., Brevard, NC, assignor to Hercules Powder Company, Wilmington, Del., a corporation of Delaware No Drawing. Filed July 6, 1960, Ser. No. 41,019 8 Claims. 01. zen-91.1

This invention relates to the curing of poly(vinyl methyl ethers).

It is known that poly(vinyl methyl ethers) can be cured by a combination of sulfur and certain organic peroxides as catalyst therefor. Such polymers have the disadvantage that they contain sulfur in both combined and free states.

In accordance with the been found that poly(vinyl methyl ether) is much more completely cured by heating a composition of poly(vinyl methyl ether) and dicumyl peroxide or its homologs and that sulfur is not necessary for effective cross-linking with this peroxide.

The dicumyl peroxide is used in an amount in the range of 0.1 to 20% of the weight of the polymer (preferably 0.5 to 10%) and incorporated in the polymer by use of the usual compounding procedures used in the rubber industry. The compounding is carried out under temperature controlled conditions so as to avoid premature cure. A temperature in the range of 50 F. to 250 F. may be safely used.

The improvement in curing is applicable to both crystalline and amorphous poly(vinyl methyl ether). The improvement is determined by change in solubility and by percent swell of the insoluble material. While uncured amorphous poly(vinyl methyl ether) is soluble in toluene, used for the determination of gel and percent swell, the crystalline poly(vinyl methyl ether) is already largely insoluble, and the increase in amount of gel and decrease in percent swell are both indicative of cure.

The preferred temperature at which curing is effected 2,984,655 Patented May 16,. 1961 temperatures as high as 700 F. may be used with short cure times so as to avoid decomposition.

The degree of cure is improved by the addition of, quinonedioxime dibenzoate or triallyl cyanurate to the the composition in an amount in the range of 0.5-20% of the polymer. The;composition may also contain fillers such as carbon black, silica, calcium carbonate, zinc oxide, and other inorganic fillers.

Examples of compositions cured in accordance with this invention with gelation tests to show degree of cure are set forth in Tables 1- and 2.

present invention, it has now The compositions of Tables 1 and 2 were prepared by dry milling the poly(vinyl methyl ether) with dicumyl peroxide and other components on a two-roll mill at about 100 F. in thecase of the amorphous polymer and at about 250 F. in the case of the crystalline polymer. The compositions were then cured in a closed mold under 500 p.s.i. Amounts of ingredients are expressed as parts by weight, and percentages are by weight.

The percent gel and percent swell were determined as follows: a weighed cylindrical sample of polymer weighing about 100 mg. was soaked 'at room temperature in an excess of toluene (30 cc.) in a closed container for 48 hours. The sample was then removed, blotted on filter paper without squeezing so as to remove toluene 0n the surface and weighed at once. The swollen sample was then dried in a current of air at room. temperature over a 72-hour period to constant weight. The weights were corrected for non-polymer content based on knowledge of components. From these figures:

Similarly, percent swell was calculated by the formula:

Corrected swollen weight-corrected dry weight Corrected dry weight X 100= percent swell No correction was applied for insolubility of the uncured crystalline polymer in toluene.

Methods for the preparation of amorphous and crystalline poly(vinyl methyl ether) are known in the art, viz., US. Patent No. 2,799,669 and British Patent No. 820,469. Both cold water soluble and cold water insoluble polylies m the range of about 250 F. to about 380 F., but mers are cured by the process of this invention.

Table I Poly(vinyl methyl ether)- A' 100 100 100 100 100 100 100 100 100 100 100 Poly(vinyl methyl ether)- O 100 100 100 100 100 100 100 100 100 Dicurnyl peroxide 5 5 1 2 4 8 1 2 4 8 1 2 4 8 l 2 4 8 Quinone dioxime dihenzoate 5 1 2 4 1 2 4 8 Cure temperature, F 320 320 320 320 320 320 0 320 320 320 320 320 320 320 320 320 320 320 320 Cure time (Minutes) 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 Percent Ge1 95 96 92 95 98 92 94 93 98 52 97 83 73 93 98 100 95 95 Percent Swell 410 1,150 840 640 520 810 510 420 350 1,470 940 1.230 1,130 620 410 390 490 335 A-amorphous, RSV 2.3.

G=crysta1liue, RSV 8.0, cold water insoluble polymer of British Patent N 0. 820,469.

Table 2 Poly(vinyl methyl ether)- Dicumyl peroxide 0 2 4 2 4 2 4 Quinone dioxlme dibenzoate 2 4 Triallyl cyanurate 2 4 High abrasion furnace black- 50 50 50 5!) 50 50 Curve temperature, "F 320 320 320 320 320 320 320 Cure time (Minutes)- 30 30 30 30 30 30 30 Percent Gel 0 87 97 99 100 103 Percent SwelL. 755 365 350 260 440 175 Tensile strength, 850 1,850 1,705 1, 450 1,750 1,400 Modulus, p.s. 220 32 350 680 240 Max. Elongation. percen 460 315 265 160 410 A'=amorphous, RSV 2.3.

The cured compositions of this invention are improved in physical properties and reduced solubility in organic solvents and are improved for many coating applications including wire coating, and for molded articles where these properties are desired. When bis,(a, t-dimethyl-p-methylbenzyl) peroxide and bis(a x-dimethyl-p-isopropylbenzyl) peroxide were substituted for dicumyl peroxide in the above examples, improvements of similar magnitude were obtained.

The homologs of dicumyl peroxide which are included in the scope of the present invention arev all peroxides of the formula in. which R and R are phenyl, and lower alkyl substituted phenyl and R R R and R are hydrogen or lower alkyl, said lower alkyl containing, 1 to 4 carbon atoms. The preferred peroxides are those. in which R R R and R are lower alkyl, and the preferred example of this group is dicumyl peroxide. Specific preferred peroxides of this invention besides dicumyl peroxide are bis(a,a-dimethyl-p-methylbenzyl) peroxide, and bis(a,a-dimethyl-p-isopropylbenzyl) peroxide, which are higher homologs. of dicumyl peroxide.

What I claim and desire to protect by Letters Patent is:

' 1. The method of curing poly(vinyl methyl ether) which comprises heating poly(vinyl methyl ether) in contact with 0.1 to 20% of a peroxide of the formula in which R and R are selected from the group con-' sisting of phenyl and lower alkyl substituted phenyl and R R R and R are selected from the group consisting of hydrogen and lower alkyl radicals, said lower alkyl containing 1 to 4 carbon atoms at a curing temperature in the range of 250 F. to 700 F.

2. The method of curing poly(vinyl methyl ether) which comprises heating poly(vinyl methyl ether) in contact with 0.1 to 20% dicumyl peroxide at a curing temperature in the range of 250 F. to 700 F.

3. The method of claim 2 in which the dicumyl peroxide is used in an amount in the range of 0.1 to 10% and the curing temperature is in the range of 250 F. to 380 F.

4. The method of claim 3 in which the poly(vinyl methyl ether) is amorphous.

5. The method of claim methyl ether) is crystalline.

6. The method of claim 3 in which 0.5 to 20% quinone dioxime dibenzoate is included in the compositionlduri'ng the curing treatment.

3 in which the poly(vinyl 7. The method of curing poly(vinyl methyl ether) which comprises compounding poly(vinyl. methyl ether) with 0.1 to 10% dicumyl peroxide at a temperature below cure temperature and subsequently heating the composition at a temperature in the range of 250 F. to. 380 F. to efiect a cure.

8. The method of claim 3 in which 0.5 to 20% tri allylcyanurate is included in the composition during the curing treatment.

References Cited in the file of this patent UNITED STATES PATENTS.

2,429,587 Schildknecht' Oct; 21, 1941 

1. THE METHOD OF CURING POLY(VINYL METHYL ETHER) WHICH COMPRISES HEATING POLY(VINYL METHYL ETHER) IN CONTACT WITH 0.1 TO 20% OF A PEROXIDE OF THE FORMULA 